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| Home > Publications database > Zur Ozonbilanz in der Troposphäre : Flugzeuggestützte Messungen von Ozon, CO und Noy |
| Home > Publications database > Zur Ozonbilanz in der Troposphäre : Flugzeuggestützte Messungen von Ozon, CO und Noy |
| Book | PreJuSER-52284 |
; ; ;
1997
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag
Jülich
Please use a persistent id in citations: http://hdl.handle.net/2128/20173
Report No.: Juel-3425
Abstract: Results obtained from 14 flights made within the European research project OCTA (McKenna et al., 1995) on board the British Research aircraft Hercules C-130 are presented and discussed. Participants within the project were besides other groups the Meteorological Research Flight (MRF) of the United Kingdom Meteorological Office (UKMO) and the ICG-2 ofForschungszentrum Jülich (FZJ, former KFA). During 4 intensives during summer 1993 and during winter/spring 1994 a suite of several chemical species, aerosol concentrations, photolysis rates and meteorological parameters were measured in the troposphere over the north Atlantic. Within this work the mixing ratios of CO, NO and NOy as well as the photolysis frequency of NO$_{2}$ were measured. A new instrument for the measurement of atmospheric CO was deployed for the first time. The measurements show that the instrument combines a high time resolution (2 s) with a high accuracy (5 ppb in 30 s, 3 $\sigma$), which makes it suitable for airborne measurements. The measurements during August 1993 took place in parallel to the NAREmeasurements (North Atlantic Regional Experiment) near the east coast of the United States. An intercomparison of the measurements of NO and NO$_{y}$ showed agreement within the experimental errors. The inlet losses for HNO$_{3}$ found in several tests during the flights were confirmed by the intercomparison. In general, no region over the north Atlantic can be regarded as truly remote from continental emissions. During the summer intensive several airmasses with enhanced mixing ratios of CO and nitrogen oxides were found, which indicates long range transport of pollutants from Europe or from the US. North of the polar front the measurements made during winter and spring 1994 showed higher mixing ratios of CO and NO$_{y}$ as compared to the measurements made south of the polar front at the same time. This confirms the effectiveness of the polar front as a barrier for transport of chemical constituents. North of the polar front, stratospheric influenced airmasses were observed in the upper free troposphere, showing a clear anticorrelation between ozone and CO as well as between ozone and water vapour. In these airmasses a correlation between NO$_{y}$ and ozone with a slope of 8 - 9 $\cdot$ 10$^{-3}$ (ppb NO$_{y}$/ppb O$_{3}$) was found, which confirmes former results obtained by Lerner et al. (1994). The measured concentrations of O$_{3}$ are compared to their equilibrium values, as calculated with a photochemical box model from the measured concentrations of H$_{2}$O, CO, NO$_{y}$ or NO, as well as T, p and jNO$_{2}$. Due to the low concentrations of non methane hydrocarbons, the cheistry scheme was simplified by including only methane and CO as ozone precursors. A cluster analysis of the continuously measured parameters was made to reduce the 2571 minute averages to 48 statistically significant groups. The cluster me ans of the parameters were used as constrain for the model calculations. The calculations were made in two ways: constraining the model by the measured NO$_{y}$ and using NO as diagnostic variable and viceversa.
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